E2250 错误，delphi7编译通过2007报错

错误：E2250 There is no overloaded version of 'UpperCase' that can be called with these arguments
代码：
begin
AStream := TStringStream.Create('');
try
SResponse := UpperCase(ReadLn);
if Pos('SMS_YWZCZX', SResponse) = 0 then Break;
        send_msgs:='1001'+'&'+'qf'+'&'+'qf'+'&'+trim(nbr)+'&'+trim(msg_content)+'&'+local_ip;
WriteLn(send_msgs);
{ read all bytes until disconnected  no length er in stream }
ReadStream(AStream, -1, True);
       AStream.Seek(0, soFromBeginning);
        if AStream.DataString='短信发送成功' then
          inc(success_count)
        else
          inc(failed_count);
        result:=true;
finally
Disconnect;
AStream.Free;
end;
delphi7编译成功，2007里面咋不行呢？